Pipe Connection Having Staggered Bolt Configuration

ABSTRACT

A pipe connection having flange members which are configured so that the bolts which secure the two flanges of the connection together are staggered axially. One embodiment comprises a first flange member, a second flange member and a set of bolts and corresponding nuts. Each flange member has bolt holes sized to accommodate the bolts. The bolts are positioned in the bolt holes, and the nuts are tightened onto the bolts to secure the first flange member to the second flange member. Each of the bolt holes has a corresponding bolt seat against which one of the bolts&#39; heads or nuts is seated, and the bolt seats of adjacent bolt holes are staggered axially (i.e., in the direction of an axis of symmetry through the flange members) so that each bolt&#39;s corresponding nut can be tightened without interference from the adjacent bolts or the corresponding nuts.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application 61/161,302, filed Mar. 18, 2009, which is incorporated by reference as if set forth herein in its entirety.

SUMMARY

This disclosure is directed to an improved design for a pipe connection that can reduce the size and weight of large, high-pressure pipe connections, thereby making the connections smaller, lighter, less expensive, and easier to manufacture, transport, install and assemble. The pipe connection incorporates one or more flange members that are configured so that the bolts which secure the two flanges of the connection together are staggered axially.

One embodiment comprises a pipe connection having a first flange member, a second flange member and a set of bolts and corresponding nuts. Each of the flange members has a plurality of bolt holes, each of which is sized to accommodate one of the bolts. The bolts are positioned in the bolt holes, and the nuts are tightened onto the bolts to secure the first flange member to the second flange member. Each of the bolt holes has a corresponding bolt seat against which one of the bolts' heads or nuts is seated, and the bolt seats of adjacent bolt holes are staggered axially (i.e., in the direction of an axis of symmetry through the flange members) so that each bolt's corresponding nut can be tightened without interference from the adjacent bolts or the corresponding nuts.

In one embodiment, the bolt seats of adjacent bolt holes are axially displaced by at least the thickness of one of the nuts. Adjacent ones of the bolts may be oriented in opposite directions. In one embodiment, the bolt seats of a first half of the bolt holes lie on a first plane and the bolt seats of a second half of the bolt holes lie on a second plane which is displaced from the first plane in the direction of the axis. The first and second planes are orthogonal to the axis of the flange members. The flange members may be swiveling flange members which include, for example, an inner portion and a collar. The inner portion has a sealing face and a rear-facing shoulder, and the collar has an outer flange portion and a forward-facing shoulder. The collar is positioned around the inner portion with the forward-facing shoulder of the collar contacting the rear-facing shoulder of the inner portion, and the outer flange portion of the collar is bolted to the opposing flange member to secure the connection.

An alternative embodiment comprises a flange member configured to be bolted to another flange member to form a pipe connection. The flange member has an outer flange portion which is substantially symmetric about an axis of the flange member and has a plurality of bolt holes through it. Each bolt hole has a corresponding bolt seat, and wherein the bolt seats are staggered in the direction of the axis.

Another alternative embodiment comprises a pipe section that is configured to be coupled to another pipe section. The pipe section includes a tubular section of pipe and a flange member connected to the end of the pipe. The flange member has an outer flange portion with a set of bolt holes through it. Each bolt hole has a corresponding bolt seat, and the bolt seats are staggered in the direction of the axis that extends through the section of pipe and the flange member.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the invention may become apparent upon reading the following detailed description and upon reference to the accompanying drawings.

FIG. 1 is a perspective view of an exemplary pipe connection.

FIG. 2 is an end view of the pipe connection of FIG. 1 showing the bolt configuration of the connection.

FIG. 3 is a cross-sectional side view of a pipe connection in accordance with one embodiment.

FIG. 4 is a detail view of the hub and weld neck area of one of the flange members of the pipe connection of FIG. 3.

FIG. 5 is a detail view of the hub and weld neck area of a flange member having a positive hub in accordance with one embodiment.

While the invention is subject to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and the accompanying detailed description. It should be understood, however, that the drawings and detailed description are not intended to limit the invention to the particular embodiment which is described. This disclosure is instead intended to cover all modifications, equivalents and alternatives falling within the scope of the present invention as defined by the appended claims.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

An improved design for a pipe connection is disclosed herein. This design can reduce the size and weight of large, high-pressure pipe connections, thereby making the connections smaller, lighter, less expensive, and easier to manufacture, transport, install and assemble.

Embodiments of the pipe connection may incorporate two distinct, unique features. First, the connection may incorporate a reverse spline hub between the outer portions of the flanges and the corresponding weld necks. Second, the connection may be configured so that the bolts that secure the two flanges of the connection together are staggered.

Pipe connections that are secured by bolts are only as strong as the bolts that hold the flanges together. The strength of the bolts is directly related to the cross-sectional area of the bolts. There are well-known calculations that are conventionally used to determine the bolt area that is required to meet the design goals of the connection. The bolt area drives the size and number of the bolts that are required to secure the connection.

Large, high-pressure connections normally require many bolts to secure the flanges of the connection to each other. Conventionally, the bolts are arranged in a circular pattern around the flanges. This is referred to as the “bolt circle”.

In a conventional connection, the flanges of the connection have all of the bolts at symmetric positions. That is, the bolts are identically positioned axially (i.e., in the direction of the connection's axis), but they are angularly displaced (with respect to the axis of the connection) on the bolt circle. Because it is necessary to provide some spacing between the bolts in order to maintain the flanges'integrity and to provide enough space to tighten the bolts, it is typically necessary to increase the size of the flanges (i.e., increase their diameters) in order to increase the bolt circle and thereby accommodate all of the necessary bolts. This increases the weight and the cost of the connection.

Increases in the size of the bolt circle also affect the stresses on the flanges. The connection typically includes a gasket that is positioned between the flanges. The gasket is normally positioned near the inner diameter of the connection. Because the bolt circle is larger than the gasket diameter, the tightening of the bolts causes the outer portions of the flanges to flex, rotating or pivoting around the gasket. The ratio of the bolt circle to the gasket diameter is referred to as the “moment arm” of the connection.

As the moment arm of the connection increases, the stresses that are placed on the flanges increase. Conventionally, it is necessary to increase the thickness of the flanges in order to withstand the increased stress. Thus, according to conventional design principles, increased bolt area leads to an increased bolt circle, which increases the moment arm, leading to increased thickness, weight and cost.

In one embodiment of the present connection, the bolts are staggered axially (in the direction of the axis of the connection) so that when a bolt extending through the flanges is tightened, the positions of the adjacent bolts do not interfere with the tightening of the first bolt. This allows the bolts to be positioned more closely to each other than would be possible using conventional design principles. Then, because the bolts can be closer to each other, the bolt circle can be reduced. The reduced size of the bolt circle results in a reduced flange diameter, a reduced moment arm, reduced flange thickness, reduced weight, and reduced cost in comparison to a conventional flange with comparable performance.

Referring to FIG. 1, a perspective view of an exemplary connection is shown. It can be seen that the two flanges (110, 111) are secured to each other by a plurality of bolts (e.g., 120-124). It can also be seen that the flanges incorporate recesses which allow alternate ones of the bolts to be displaced axially with respect to their neighbors. Thus, the head of a bolt (e.g., 130) can be positioned within a recess (e.g., 140) so that it does not interfere with the tightening of a nut (e.g., 151) on an adjacent bolt. In this embodiment, the seats for half of the bolts are on a first plane, while the seats for the remainder of the bolts are on a second plane.

In this embodiment, successive bolts are oppositely oriented so that, for a first bolt, the head is seated against a first one of the flanges and the corresponding nut is seated against the second one of the flanges, while for the adjacent bolt, the head is seated against the second flange and the corresponding nut is seated against the first flange. It should be noted that adjacent bolts need not be oriented in opposite directions if they can nevertheless be tightened on opposite ends (e.g., a wrench tightens the nut on a first bolt, and tightens the heads of adjacent bolts).

Referring to FIG. 2, an end view of the connection is shown. In this figure, the axis of the connection is orthogonal to the page. It should be noted that, while the bolt heads are depicted in FIGS. 1 and 2 as being round, they may also be hexagonal or otherwise shaped to prevent the bolts from rotating when seated in the recesses. It can also be seen that the bolts are regularly spaced on bolt circle 210. The connection is substantially symmetric about its axis (160 in FIG. 1).

Because adjacent bolts are staggered axially and oriented in opposite directions, the bolts can be placed closer together than conventionally configured bolts. In other words, the need to be able to position tools between adjacent bolts in order to tighten them is removed as a design constraint, so the bolts can be closer together, resulting in a smaller bolt circle. The smaller bolt circle, in turn, results in smaller-diameter flanges, reduced moment arms for flexion/rotation of the flanges, reduced flange thickness, reduced weight and reduced cost.

It should be noted that the flanges of FIGS. 1 and 2 may be of various different types and may include many different features that are independent of the staggered bolt configuration that is illustrated in the figures. For instance, the flanges may be solid or they may contain multiple pieces, they may be swivel or misalignment flanges, they may have positive or reverse hubs, and so on.

Referring to FIG. 3, a cross-sectional side view of an exemplary connection is shown. The illustrated connection is a swiveling connection that employs a solid bolted flange member 310 and a swiveling flange member 320. Swiveling flange member 320 includes an inner flange portion 321 and a swiveling collar portion 322. Swiveling collar portion 322 rotates around inner flange portion 321 to facilitate alignment of the bolt holes in the collar with the bolt holes in solid flange 310. Swiveling collar 322 is bolted to solid flange 310 to secure the connection. A forward-facing shoulder 323 on swiveling collar 322 contacts a complementary rear-facing shoulder 324 on inner flange portion 321 to secure the inner flange portion against solid flange 310. (Here, “forward-facing” means facing toward the sealing face of the flange, while “rear-facing” means facing away from the sealing face of the flange.) Gasket 340 is positioned between the sealing faces of the flange members to ensure a good seal.

It can be seen in FIG. 3 that the seats for the bolts (e.g., 315, 316) are staggered axially by an amount that is sufficient to eliminate overlap between the nut on one bolt (e.g., 381) and the adjacent bolt (e.g., 382). It can also be seen in FIG. 3 that flange member 310 does not have a conventional hub between the body 370 of the flange member and the weldneck 360. Solid flange member 310 instead employs a reverse spline hub 330 to minimize stresses on the flange resulting from flexion of the flange around gasket 340. This is shown in more detail in FIG. 4.

In a flange having a conventional hub (e.g., as shown in FIG. 5), a positive hub 510 is formed between the outer, bolted portion of the flange 520 and the weldneck 530. The purpose of the hub is to reduce stress on the weld neck when the flange is secured to another flange, causing it to flex, rotating the bolted portion of the flange 520 (counterclockwise in the figure) around the gasket 540. In the absence of hub 510, the resulting stresses tend to cause the flange to fail where the bolted portion of the flange 520 meets weldneck 530. Hub 510 is intended to reinforce this failure point, but the hub may simply transfer the stresses, causing the flange to fail at the junction between the hub and the weldneck.

In the connection of FIG. 3, flange 310 uses what may be referred to as a reverse hub. Rather than tapering from a larger diameter to a smaller diameter as the distance from the face 380 of the flange increases (a “positive” hub), the diameter of the flange tapers from larger to smaller as the distance from the face 380 of the flange decreases (a “reverse” hub). The conventional, positive hub is shown in FIG. 5, and is illustrated by the dashed line in FIG. 4 for purposes of comparison to the reverse hub.

Reverse hub 330 is referred to above as a reverse spline hub. This indicates that reverse hub 330 follows a spline curve which minimizes the stress caused by the rotation of the bolted portion of the flange about the gasket. In this case, the spline curve has been empirically determined to minimize the stress resulting from rotation of the flange about the gasket.

It has been found that the reverse spline hub reduces stresses induced by the rotation of flange 111 so effectively that the flange can be made thinner (i.e., thickness T can be reduced), as a greater amount of rotation of the flange can be tolerated without exceeding stress limits at the junction between the hub and the weldneck. Thus, the reverse spline reduces the size and weight of the connection, both by eliminating the material that would form the hub in a conventional connection, and by eliminating material when the thickness of the flange is reduced.

It should be noted that the embodiments described above are exemplary, and are intended to be illustrative of the many embodiments that are possible. Alternative embodiments may incorporate only selected ones of the features described above, or they may have variations of these features. For example, alternative embodiments may or may not include swiveling flange members or reverse hubs. The various embodiments of the invention may be connected (e.g., welded) to pipe sections, or they may be separate from the pipe sections.

The benefits and advantages which may be provided by the present invention have been described above with regard to specific embodiments. These benefits and advantages, and any elements or limitations that may cause them to occur or to become more pronounced are not to be construed as critical, required, or essential features of any or all of the claims. As used herein, the terms “comprises,” “comprising,” or any other variations thereof, are intended to be interpreted as non-exclusively including the elements or limitations which follow those terms. Accordingly, a system, method, or other embodiment that comprises a set of elements is not limited to only those elements, and may include other elements not expressly listed or inherent to the claimed embodiment.

The preceding description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein and recited within the following claims. 

1. A pipe connection comprising: a first flange member; a second flange member; and a plurality of bolts, wherein each bolt has a corresponding nut threaded thereon; wherein each of the first and second flange members has a plurality of bolt holes therethrough, wherein each bolt hole is sized to accommodate one of the bolts therethrough; and wherein each of the bolt holes has a corresponding bolt seat, wherein in each flange member the bolt seats of adjacent bolt holes are staggered in the direction of an axis of symmetry through the flange members; wherein each of the plurality of bolts is positioned through one of the bolt holes in each of the first and second flange members, securing the first flange member to the second flange member.
 2. The pipe connection of claim 1, wherein the bolt seats of adjacent bolt holes are axially displaced by a distance at least as great as the thickness of one of the nuts.
 3. The pipe connection of claim 1, wherein adjacent ones of the bolts are oriented in opposite directions.
 4. The pipe connection of claim 1, wherein for each flange member, the bolt seats of a first half of the bolt holes lie on a first plane and the bolt seats of a second half of the bolt holes lie on a second plane which is displaced from the first plane in the direction of the axis.
 5. The pipe connection of claim 4, wherein the first and second planes are orthogonal to the axis.
 6. The pipe connection of claim 1, wherein at least one of the flange members comprises a swiveling flange member.
 7. The pipe connection of claim 6, wherein the swiveling flange member comprises an inner portion and a collar, wherein the inner portion includes a sealing face and a rear-facing shoulder, wherein the collar includes the outer flange portion and a forward-facing shoulder, wherein the collar is positioned around the inner portion with the forward-facing shoulder of the collar contacting the rear-facing shoulder of the inner portion.
 8. A first flange member configured to be bolted to a second flange member to form a pipe connection, the first flange member comprising: an outer flange portion which is substantially symmetric about an axis, the outer flange portion having a plurality of bolt holes therethrough; wherein each bolt hole has a corresponding bolt seat at an opening of the bolt hole, and wherein the bolt seats are staggered in the direction of the axis.
 9. The flange member of claim 8, wherein the bolt seats of adjacent bolt holes are axially displaced by a distance at least as great as the thickness of a nut.
 10. The flange member of claim 8, wherein the bolt seats of a first half of the bolt holes lie on a first plane and the bolt seats of a second half of the bolt holes lie on a second plane which is axially displaced from the first plane.
 11. The flange member of claim 8, wherein the first and second planes are orthogonal to the axis.
 12. The flange member of claim 8, wherein the first flange member comprises a swiveling flange member.
 13. The flange member of claim 8, wherein the swiveling flange member comprises an inner portion and a collar, wherein the inner portion includes a sealing face and a rear-facing shoulder, wherein the collar includes the outer flange portion and a forward-facing shoulder, wherein the collar is positioned around the inner portion with the forward-facing shoulder of the collar contacting the rear-facing shoulder of the inner portion.
 14. A pipe section configured to be coupled to another pipe section, wherein the pipe section comprises: a tubular section of pipe; and a flange member connected to an end of the pipe, wherein the flange member includes an outer flange portion having a plurality of bolt holes therethrough, wherein each bolt hole has a corresponding bolt seat at an opening of the bolt hole, and wherein the bolt seats are staggered in the direction of an axis of symmetry that extends through the section of pipe and the flange member.
 15. The pipe section of claim 8, wherein the bolt seats of adjacent bolt holes are axially displaced by a distance at least as great as the thickness of a nut.
 16. The pipe section of claim 8, wherein the bolt seats of a first half of the bolt holes lie on a first plane and the bolt seats of a second half of the bolt holes lie on a second plane which is axially displaced from the first plane.
 17. The pipe section of claim 16, wherein the first and second planes are orthogonal to the axis.
 18. The pipe section of claim 8, wherein the first flange member comprises a swiveling flange member.
 19. The pipe section of claim 18, wherein the swiveling flange member comprises an inner portion and a collar, wherein the inner portion includes a sealing face and a rear-facing shoulder, wherein the collar includes the outer flange portion and a forward-facing shoulder, wherein the collar is positioned around the inner portion with the forward-facing shoulder of the collar contacting the rear-facing shoulder of the inner portion. 